CN110572187B

CN110572187B - Networking method for broadband power line communication network

Info

Publication number: CN110572187B
Application number: CN201910866346.2A
Authority: CN
Inventors: 金鑫; 肖勇; 黄博阳; 胡珊珊
Original assignee: China Southern Power Grid Co Ltd; Research Institute of Southern Power Grid Co Ltd
Current assignee: China Southern Power Grid Co Ltd; Research Institute of Southern Power Grid Co Ltd
Priority date: 2019-09-12
Filing date: 2019-09-12
Publication date: 2021-09-03
Anticipated expiration: 2039-09-12
Also published as: CN110572187A

Abstract

The invention discloses a networking method for a broadband power line communication network, which comprises the following steps: when any STA equipment of any network is in network access operation, monitoring a period of continuous time, and judging whether a beacon frame of any network is received in the continuous time; if the beacon frame is received, judging whether the beacon frame of only one network is received; and if the beacon frames of at least two networks are received, the STA equipment sends a network access request message to CCO equipment of the network closest to the MAC address of the STA equipment. The networking method enables the STA equipment to reasonably select the received beacon frame of the network when the STA equipment accesses the network, reduces the number of messages sent by the STA equipment to the non-corresponding network CCO equipment through the selection mode of the MAC address distance, avoids the waste of useless messages, reduces the burden of a channel in the network accessing process, and improves the quality of channel transmission and the utilization rate of channel resources.

Description

Networking method for broadband power line communication network

Technical Field

The invention belongs to the technical field of broadband power line communication, and particularly relates to a networking method of a broadband power line communication network.

Background

The PLC (Power Line Communication) is a Communication mode using a Power Line as a transmission medium, is mainly applied to remote automatic meter reading, automatic control of a Power distribution network, home internal interconnection, network access in an intelligent cell and a last kilometer of multimedia Communication, and has the characteristics of high construction speed, low investment, no need of indoor wiring, and the like. In recent years, the development of BPL (broadband power line) related technology has increased the data transmission rate of power line communication, and in particular, the development of orthogonal frequency division multiplexing technology has enabled high-speed PLC. The power line communication has wide application prospect under the advantages of wide distribution of power lines, no need of extra wiring and low cost.

In the network networking method in the prior art, before STA (Station) equipment fails to access the network, the STA equipment sends a network access request after receiving a beacon frame of any network; after receiving a network Access request sent by an STA device, a Central Coordinator (CCO) sends a downlink message to reject Access to the network of the STA device if an MAC (Media Access Control) address of the STA device is not in a white list, which may cause waste of useless uplink and downlink messages, prolong networking time, and cause channel congestion.

Disclosure of Invention

The invention aims to provide a networking method of a broadband power line communication network, which aims to solve the problem of waste of uplink and downlink messages and avoid channel congestion.

In order to achieve the purpose, the invention adopts the following technical scheme:

a networking method of a broadband power line communication network comprises the following steps:

when any STA equipment of any network is in network access operation, monitoring a period of continuous time, and judging whether a beacon frame of any network is received in the continuous time;

if the beacon frame is received, judging whether the beacon frame of only one network is received;

and if the beacon frames of at least two networks are received, the STA equipment sends a network access request message to the CCO equipment of the network which has the closest distance with the MAC address of the STA equipment, namely the MAC address difference is the smallest.

Optionally, if the beacon frame is received, determining whether only one network is received after the beacon frame, further includes the following steps:

if the beacon frame is not received, returning to the step of monitoring a period of continuous time when any STA equipment of any network performs network access operation, and judging whether the beacon frame of any network is received in the continuous time.

Optionally, the STA device sends a network access request message to a CCO device of a network having a closest distance to the MAC address of the STA device, that is, a minimum MAC address difference value, where the method for calculating the MAC address distance between the STA device and the network includes:

setting the continuous time for the STA equipment to monitor the beacon from the CCO equipment center or the discovery beacon of the accessed STA equipment as T;

detecting Beacon frames of N different networks in a T continuous time period, and respectively marking the Beacon frames as { Beacon _ i }, wherein i is more than or equal to 1 and less than or equal to N, and the detected central Beacon of the CCO equipment only has the MAC address of the CCO equipment, and the decimal form of the MAC address is marked as CCO _ i; the intercepted discovery beacon of the accessed STA equipment comprises the MAC address of the CCO equipment of the network and the MAC address of part of the accessed STA equipment of the network;

if there are M accessed STA devices, the decimal form of the MAC address of the CCO is recorded as CCO _ i, the decimal form of the MAC address of the STA device is respectively recorded as STA _ j, wherein j is more than or equal to 1 and is less than or equal to M; the decimal form of the MAC address of the intercepted STA equipment is recorded as STA _ a;

then the Central Beacon of the CCO device is heard in T consecutive time periods, that is, the address distance between the network of the Central Beacon and the STA device is:

Network_address＝|STA_a-CCO_i|；

if the Discover Beacon of the accessed STA device is sensed in the T continuous time period, the address distance between the network of the discovery Beacon and the STA device is as follows:

optionally, after the STA device sends a network access request message to the CCO device of the network corresponding to the beacon frame if the beacon frame of only one network is received and sends a network access request message to the CCO device of the network closest to the MAC address of the STA device if the beacon frames of at least two networks are received, the method further includes the following steps:

the STA equipment judges whether a network access request reply message is received within set time;

and if the network access request reply message is received within the set time, setting the state of the STA equipment as 'network access'.

Optionally, after the STA device determines whether to receive the network access request reply message within a set time, the method further includes the following steps:

if the network access request reply message is not received within the set time, judging whether the STA equipment receives a network access request refusal message within the set time;

if the network access request rejection message is received within the set time, after waiting for a preset time, returning to execute the network access operation of any STA equipment of any network, monitoring for a continuous time, and judging whether a beacon frame of any network is received within the continuous time.

Optionally, the preset time is equal to 150 seconds.

Optionally, if the network access request reply message is not received within the set time, after determining whether the STA device receives a network access request reject message within the set time, the method further includes the following steps:

if the network access request refusing message is not received within the set time, judging whether other networks can apply for joining;

if other networks can apply for joining, selecting other networks which are not requested and have the nearest distance with the MAC address of the STA equipment, sending a network access request message to CCO equipment of the network, and then executing whether the STA equipment receives a network access request reply message within set time.

Optionally, if the network access request rejection message is not received within the set time, after determining whether there is another network that can apply for joining, the method further includes the following steps:

if no other network can apply for joining, the method returns to execute that any STA equipment of any network monitors a period of continuous time when performing network access operation, and judges whether a beacon frame of any network is received in the continuous time.

Optionally, if the beacon frame is received, determining whether only one network is received after the beacon frame, further comprising the following steps:

and if the beacon frame of only one network is received, sending a network access request message to the CCO equipment of the network corresponding to the beacon frame.

Compared with the prior art, the embodiment of the invention has the following beneficial effects:

the networking method of the broadband power line communication network provided by the embodiment of the invention can enable the STA equipment to reasonably select the received beacon frame of the network when the STA equipment accesses the network, and reduce the number of messages sent by the STA equipment to the non-corresponding network CCO equipment through the selection mode of the MAC address distance, thereby avoiding the waste of useless messages, reducing the burden of channels in the network accessing process and improving the quality of channel transmission and the utilization rate of channel resources.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so that those skilled in the art can understand and read the present invention, and do not limit the conditions for implementing the present invention, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the functions and purposes of the present invention, should still fall within the scope covered by the contents disclosed in the present invention.

Fig. 1 is a diagram of a standard-based Open System Interconnection (OSI) seven-layer model of a broadband carrier communication network protocol stack according to an embodiment of the present invention.

Fig. 2 is a topology diagram of a broadband carrier communication network according to an embodiment of the present invention.

Fig. 3 is a time slot division diagram of a beacon period according to an embodiment of the present invention.

Fig. 4 is a time slot division diagram of a beacon period according to an embodiment of the present invention.

Fig. 5 to 10 are flowcharts of a method for networking a broadband power line communication network according to an embodiment of the present invention.

Detailed Description

In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Please refer to fig. 1. The broadband carrier communication network protocol stack defines 3 layers of a physical layer, a data link layer and an application layer based on a standard Open System Interconnection (OSI) seven-layer model.

The data link layer is divided into a network management sublayer and a media access control sublayer. The data link layer directly provides transmission service for the application layer, and can also be extended to interface with standard TCP/IP to realize standard IP network communication.

The broadband carrier communication network topological diagram is shown in fig. 2, and the networking process of the BPL is mainly divided into three parts, namely multi-network inter-network coordination, single-network networking and network maintenance.

Multi-network inter-network coordination: the specific flow of the multi-network inter-network coordination is as follows:

1. after the CCO is started, network monitoring is performed for a period of time, and whether a working broadband carrier communication network exists around the CCO is judged. For the broadband carrier communication network which is already in operation, the inter-network coordination frame should be periodically sent so that other CCOs which are powered up later can monitor.

2. If the inter-Network coordination frame of the neighbor Network is received within the CCO monitoring time, negotiation needs to be performed according to a certain priority principle according to information such as a Short Network Identifier (SNID) and a time slot carried in the inter-Network coordination frame; if no inter-network coordination frame is monitored, the CCO can work independently.

3. And then, carrying out bandwidth coordination, and staggering the beacon time slots of different networks as orderly as possible according to a bandwidth negotiation principle, so that not only is the collision of the beacon time slots ensured, but also the periodicity of beacon time slot transmission is ensured.

Single-network networking: the process of individual networking is mainly that the CCO triggers a network access request of the STAs layer by sending a central beacon and scheduling discovery beacon transmission, and sending a proxy beacon, so as to complete the whole networking process. The networking process is divided into three parts, namely, the networking behavior of a CCO (central office), the networking behavior of a PCO (Proxy Coordinator) and the networking behavior of an STA.

1. Networking behavior of CCO

After the coordination is successful, the CCO starts networking and sends a central beacon; the CCO needs to arrange beacon TDMA (Time division multiple access) slots and CSMA (Carrier sense multiple access) slots in the central beacon. The beacon TDMA slot is used to indicate that the CCO, PCO, or STA transmits a beacon.

If a first-level site requests to access the network, the CCO needs to perform identity authentication on the site requesting to access the network through a white list. Then, the CCO may notify the STA of the processing result of the association request by sending an association indication message.

After the first-level station accesses the network, the CCO may arrange a beacon slot to allow the newly-accessed first-level station to send a discovery beacon. The sending of the discovery beacon can trigger secondary stations around the new network-accessing station to initiate a request for associating network access. After the second-level site accesses the network, the CCO may arrange a beacon time slot, allow the newly accessed second-level site to send a discovery beacon, and trigger the third-level sites around the second-level site to initiate an association network access request. The above-mentioned steps are circulated, so that the STA station of the highest hierarchy furthest away from the CCO joins the network.

2. After the STA is powered on, the STA may receive messages of multiple networks (with different SNIDs), and the STA station may select a network with a better signal from the multiple networks according to the multiple network preference flag, and use the network as an access target network of the STA station, or select a network discovered for the first time as an access target network.

3. Networking behavior of PCOs

After the STA successfully accesses the network, if the STA is scheduled by the CCO to send a discovery beacon, the STA may be selected by the next station to become a proxy station of the next station;

when an STA is confirmed to be a proxy station by the CCO, the CCO allocates a beacon time slot of the STA and indicates the STA to send a proxy beacon;

when an STA accesses the network through the proxy station, the CCO carries the processing result of the association request in an association confirmation message and sends the association confirmation message to the proxy station of the STA. After the processing is completed, the proxy station needs to notify the content in the association confirmation message to the STA through the association indication message.

Network maintenance: the specific process of network maintenance is as follows:

1. in the networking process, each station can sense own neighbor stations according to the received discovery beacons and record the neighbor stations to form a discovery list. The relay route of the station can be selected in the discovery list of the station.

2. If each site broadcasts and publishes the discovery list of the site, the more comprehensive network topology information is formed, and the sites can find more appropriate routes.

3. After networking is completed, the discovery list messages including the CCO and all the STAs accessing the network need to be sent periodically, and the discovery list messages carry information such as the discovery list of the local station.

4. And the proxy site (PCO) sends the site activity information in the locally maintained discovery list to the CCO through the heartbeat detection message with a fixed period.

BPL channel access mechanism

The broadband carrier communication network uses a channel access mechanism based on a beacon frame, the CCO periodically transmits the beacon frame, and the beacon frame comprises planning information of beacon time slots, TDMA time slots, CSMA time slots, binding CSMA time slots and the like in a beacon period allocated by the CCO. The sub-nodes in the broadband carrier communication network must follow the time slots allocated by the CCO to perform channel access. The slot division of the beacon period is shown in fig. 3.

Generally, timeslots explicitly allocated to a CCO or a specific STA, such as beacon slots and TDMA slots, are collectively referred to as non-contention slots (TDMA slots); the CSMA slot and the binding CSMA slot, etc. are slots not designated by a user, and slots to be used by STAs having a need for contention are collectively referred to as contention slots (CSMA slots).

When a plurality of broadband carrier communication networks coexist and interfere with each other, time slot coordination needs to be performed between the CCOs.

The CCO needs to consider the phase line factor of the power line when performing channel access. The STA on different powerline phase lines also needs to consider the powerline phase line factors when communicating with the CCO. And selecting the corresponding time slot to communicate with the CCO according to the phase line where the phase line is positioned.

When the CCO plans the time slot, the binding CSMA time slot can be allocated according to the service requirement, the time slot is solely occupied by a certain service, and all the STAs related to the service can compete to send the message of the service in the binding CSMA time slot.

Beacon mechanism

There are three types of beacon frames in a broadband carrier communication network: central beacons, proxy beacons and discovery beacons. Beacon frames must be transmitted in beacon slots. Beacon slots are allocated by the CCO, and the allocation needs to indicate the corresponding slots that can be used by a particular STA. Where both the central beacon and the proxy beacons must be transmitted in each beacon period. Discovery of beacons requires each STA to transmit at least two beacon frames every 170 second time period since joining the network. Upon determining that the CCO designates that it transmits a beacon frame in a certain time slot after receiving the beacon frame, the STA must transmit the corresponding beacon frame in the corresponding time slot.

Central beacon

The central beacon is generated by the CCO, and the central beacon contains the network reference time NTB of the current broadband carrier communication network, and notifies STAs in the network in real time through the BTS field in the beacon frame. In a single broadband carrier communication network, a central beacon is sent in a fixed period, and the sending period can be customized; in a scenario where multiple broadband carrier communication networks coexist, the transmission time slot of the central beacon of the CCO needs to be coordinated among the CCOs of the multiple broadband carrier communication networks according to a certain principle.

Proxy beacon

The proxy beacon is transmitted by the proxy station (PCO), contains the entire slot schedule content of the central beacon, and carries the basic attributes of the proxy STA.

The proxy station must transmit the proxy beacon according to the beacon slot specified in the central beacon.

After receiving the proxy beacon, the STA that is not accessing the network may initiate a request for joining the network according to the contents of time slot arrangement and the like in the proxy beacon.

Discovery beacon

Discovery beacons are transmitted by the STA and must be transmitted within the beacon slot assigned to the STA by the CCO.

The discovery beacon is mainly used for discovering possible hidden STAs around. The beacon contains contents such as contention slot scheduling for hiding STAs from joining the network.

After receiving the discovery beacon, the STA that is not accessing the network may initiate a request to join the network according to the contents of time slot arrangement and the like in the discovery beacon.

Beacon slot management

The three roles of CCO, PCO and STA are consistent with the management algorithm of the time slot in the beacon. And the CCO allocates the time slots in the beacon period, fills the time slot allocation entries in the beacon according to a uniform algorithm, and notifies the stations such as the PCO, the STA and the like through beacon transmission. The resolution of the slot allocation entries in the beacon by the PCO and the STA also follows a unified algorithm.

As shown in fig. 3, the beacon period is divided into four different slots, namely a beacon slot, a CSMA slot, a TDMA slot, and a bonding CSMA slot. Since the present invention relates only to beacon slots, only beacon slots will be described herein.

Throughout the beacon period, the beacon slots are typically divided as shown in fig. 4.

Beacon time slot

As shown in fig. 4, the central beacon slot must be divided from time 0, and if there are a plurality of slots, the slots are sequentially divided according to the phase line, and as shown in fig. 4, a, B, and C indicate central beacon slots into which three CCOs are divided. The CCO needs a central beacon transmission on the three ABC phases.

When the proxy beacon slot is divided, the calculation is started after the central beacon slot needs to be shifted.

When the discovery beacon slot is divided, the calculation is started after the central beacon slot and the proxy beacon slot need to be shifted.

The embodiment provides a networking method for a broadband power line communication network, which can solve the problem of waste of the following uplink and downlink messages.

The method can be used for the STA equipment to select a certain network to join in the multi-network environment and initiate an association request to the CCO. After receiving the association confirmation message or the association indication message, the STA equipment selects other networks to join if the CCO refuses the STA to join the network. The total beacon period is divided into four different time slots.

Specifically, the networking method for the broadband power line communication network provided in this embodiment is based on the following preconditions:

1. the broadband power line communication network networking is that under a multi-network environment, PLC devices of different networks are networked together.

2. In each network, there is only one CCO device and several STA devices.

3. The SNID negotiation between the network CCO devices is completed, the SNID of each network is determined, and the independent and stable networking of each broadband communication network is ensured.

4. The beacon time slots among the networks are staggered in order according to the bandwidth coordination principle.

5. STA devices of each network are provided by the same vendor, and device MAC addresses produced by the same vendor are associated. It should be noted that the MAC address has a length of 48 bits (6 bytes), and is usually represented by 12 16-ary numbers, such as: 00-16-EA-AE-3C-40 is a MAC address, where the first 6-digit 16-ary number 00-16-EA represents the number of the network hardware manufacturer, which is assigned by IEEE (institute of electrical and electronics engineers), and the second 6-digit 16-ary number AE-3C-40 represents the serial number of a certain network product (e.g., network card) manufactured by the manufacturer. MAC addresses are unique throughout the world as long as their own MAC address is not changed. In a descriptive sense, the MAC address is just like the ID card number on the ID card, and has uniqueness

6. The beacon frame time interval for the STA devices in each network to receive each network is very small.

7. STA equipment in the broadband power line network has a network access waiting time threshold.

Further, the networking method of the broadband power line communication network specifically comprises the following steps:

and after receiving the beacon frame, any STA equipment in any neighbor network selects a network closest to the MAC address of the STA equipment to access the network.

That is, in the multi-network environment, after receiving the beacon frame, if there are multiple optional networks (i.e., multiple beacon frames are received before sending the network entry request message) in any STA device in any neighbor network, the STA device selects the network closest to the MAC address of the STA device, that is, the network with the smallest MAC address difference, to enter the network.

Therefore, after the STA device in any network listens to the beacon frame sent by any network, the STA device selects a network that is relatively closer to the MAC address of the network device to perform network access operation by analyzing the MAC address information of the network device carried in the beacon frame.

The specific method for calculating the MAC address distance between the STA equipment and the network is as follows:

in the first step, the continuous time for the STA device to listen to the central beacon from the CCO device or the discovery beacon of the accessed STA device is set as T.

Secondly, detecting N Beacon frames of different networks in a T continuous time period, and respectively marking the detected Beacon frames as { Beacon _ i }, wherein i is more than or equal to 1 and is less than or equal to N; the central beacon of the intercepted CCO device has only the MAC address of the CCO device, in decimal form denoted CCO _ i. The intercepted discovery beacon of the accessed STA device comprises the MAC address of the CCO device of the network and the MAC address of part of the accessed STA device of the network.

Thirdly, if M pieces of accessed STA equipment are arranged, marking the decimal form of the MAC address of the CCO as CCO _ i, and respectively marking the decimal form of the MAC address of the STA equipment as STA _ j, wherein j is more than or equal to 1 and is less than or equal to M; the MAC address of the overheard STA device is denoted in decimal form as STA _ a.

Fourthly, the address distance between the network of the Central Beacon which listens to the CCO device and the STA device in the T continuous time period is as follows:

Network_address＝|STA_a-CCO_i|

fifthly, if the detected distance between the network of the Discover Beacon of the accessed STA equipment and the address of the STA equipment in the T continuous time period is as follows:

therefore, the address distance between each network and the STA equipment is calculated according to a formula, and finally the closest network is selected for network access operation.

Referring to fig. 5, in particular, in the present embodiment, the method for networking a broadband power line communication network includes the following steps:

s1, when any STA device of any network is in network access operation, monitoring a period of continuous time, and judging whether a beacon frame of any network is received in the continuous time;

s2, if the beacon frame is received, judging whether the beacon frame of only one network is received;

s3, if the beacon frames of at least two networks are received, the STA device sends a network access request message to the CCO device of the network having the closest MAC address distance to the STA device, that is, the MAC address difference is the smallest.

Before step S1, the following preparation is required:

the PLC equipment is initialized firstly, and the CCO equipment and the STA equipment are powered on; under the multi-network environment, inter-network coordination is carried out among the networks; after the inter-network coordination is successful, the process may proceed to step S1.

Further, please refer to fig. 6.

If the beacon frame is received, judging whether the beacon frame of one network is received, and further comprising the following steps:

and S4, if the beacon frame of only one network is received, sending a network access request message to the CCO equipment of the network corresponding to the beacon frame.

Further, please refer to fig. 7.

The steps of, if the beacon frame of only one network is received, sending a network access request message to a CCO device of the network corresponding to the beacon frame, and if the beacon frames of at least two networks are received, after the STA device sends a network access request message to a CCO device of the network closest to the MAC address of the STA device, further include:

s5, the STA equipment judges whether a network access request reply message is received within a set time;

and S6, if the network access request reply message is received within the set time, setting the state of the STA equipment as 'network access already'.

Further, please refer to fig. 8.

After the STA device determines whether to receive a network access request reply message within a set time, the method further includes the following steps:

s7, if the network access request reply message is not received within the set time, determining whether the STA device receives a network access request reject message within the set time;

and S8, if the network access request rejection message is received within the set time, after waiting for a preset time, returning to execute the operation of any STA device of any network for network access, monitoring for a continuous time, and judging whether a beacon frame of any network is received within the continuous time.

Further, please refer to fig. 9.

If the network access request reply message is not received within the set time, the method further comprises the following steps after judging whether the STA equipment receives a network access request refusal message within the set time:

s9, if the network access request refusing message is not received in the set time, judging whether other networks can apply for joining;

s10, if there is any other network that can apply for joining, selecting other network that is not requested and has the closest distance to the MAC address of the STA device, sending a network access request message to the CCO device of the network, and then executing whether the STA device receives a network access request reply message within a set time.

Please refer to fig. 10.

If the network access request rejection message is not received within the set time, after judging whether other networks can apply for joining, the method further comprises the following steps:

and S11, if no other network can apply for joining, returning to the step of monitoring a period of continuous time when any STA equipment of any network performs network access operation, and judging whether a beacon frame of any network is received in the continuous time.

In summary, the networking method for the broadband power line communication network according to the embodiment of the present invention reduces useless network access application messages, is beneficial to reducing control overhead, and reduces network access delay: the method can lead the STA equipment to reasonably select the received beacon frame of the network when the STA equipment accesses the network, reduces the number of messages sent by the STA equipment to the non-corresponding network CCO equipment through the selection mode of the MAC address distance, avoids the waste of useless messages, simultaneously reduces the burden of a channel in the network accessing process, improves the quality of channel transmission and improves the utilization rate of channel resources.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A networking method for a broadband power line communication network is characterized by comprising the following steps:

if the beacon frames of at least two networks are received, the STA equipment sends a network access request message to CCO equipment of the network which has the shortest distance with the MAC address of the STA equipment, namely the MAC address difference value is the smallest;

if the beacon frame of only one network is received, sending a network access request message to CCO equipment of the network corresponding to the beacon frame;

if the network access request reply message is received within the set time, setting the state of the STA equipment as 'network access already';

if the network access request rejection message is received within the set time, after waiting for a preset time, returning to execute the network access operation of any STA equipment of any network, monitoring a continuous time, and judging whether a beacon frame of any network is received within the continuous time;

if other networks can apply for joining, selecting other networks which are not requested and have the closest distance with the MAC address of the STA equipment, sending a network access request message to CCO equipment of the network, and then executing whether the STA equipment receives a network access request reply message within set time;

if no other network can apply for joining, returning to execute that any STA equipment of any network monitors a period of continuous time when carrying out network access operation, and judging whether a beacon frame of any network is received in the continuous time;

the STA equipment sends a network access request message to CCO equipment of a network which is closest to the MAC address of the STA equipment, namely the MAC address difference is minimum, and the calculation method of the MAC address distance between the STA equipment and the network comprises the following steps:

Network_address＝|STA_a-CCO_i|；

2. the method according to claim 1, wherein said determining whether only one network receives the beacon frame if the beacon frame is received, further comprises: